Method of rubberizing fibrous material and article produced thereby



Patented Dec. 9, 1930 UNITED STATES" PAT-Eur OFFICE ERNEST norxmsou, onNEW YORK, N. Y.

METHOD OF RUBBERIZING FIBROUS MATERIAL AND ARTICLE PRODUCED THERE BY NbDrawing. Application filed June 21,

m foi this purpose rubber doughs, cements, and

also latex in substantially the concentration in which it is obtainedfrom the trees. The rubberized sheet may be used in sheet form or cutand plied up or otherwise joined in the making of various articles suchas tires, hose,

belting, Waterproofedclothing, gloves, footwear, etc. When coating witha material such as the previously employed solutions of milled orbroken-down rubber in organic solvents, or latex in substantially itsnatural concentration, the coating material strikes through orimpregnates the sheet or other article in varying degree depending onthe conditions. As a result the flexibility of the sheet or article islessened, due to the bonding together of the fibres or threads of thematerial bv the rubber depositedin its interstices. It has also beenfound that material rubberized on one side by the use of thin latexdeteriorates more rapidly than a sheet of rubber alone, the theoryadvanced in explanation of this being that the side of the rubber nextto and penetrating the fibrous material has a much greater-area exposedto oxidation through air'entering the material than in the case of aplain rubber sheet, and this appears to be substantiated by the factthat in the case of double texture. proofed goods, in which there isfibrous material on both sides of the rubber, the deterioration is morerapid than in the case of single texture material. In addition latex inits natural concentration or as heretofore compounded for spreading hasbeen of such fluidity that it cannot be successfully used on the usualtypes of spreader machines at present employed for 1924. Serial No.721,591.

spreading rubber doughs. Another; disadvantage is that when ordinarylatex or rubber cement is being used for coating, more particularly whenthe coating is to be applied by a dipping or sprayingoperation, thedeposit of rubber obtained on the material is relatively thin, and wherea heavier coating is desired the operation must be repeated, in-

volving considerable loss of time and labor in,

drying the material between dips.

For certain articles of manufacture the above-mentioned striking throughor impre nation of the fibrous material may not be 0%- jectionable andmay even be particularly desirable. For instance in the case of tires,the great strength and resistance to stripping obtained by impregnationwith latex is an advantage, and as the fibrous material in the tire iscompletel encased in rubber, the'comparatively rapi ageing which occursin rubberized fibrous material having its fibres exposed to the air doesnot occur. vMoreover. as the tire casing is comparatively stiif byreason of being built up of numbers of layers of. fabric and rubber andis not required to flex except under relatively great pressure ascompared for instance to rubberized clothing, the loss in flexibilitydue to the impregnation of the material is relatively small and notobjectionable.

In many rubberized articles, however, the impregnation of the fibrousmaterial and the results thereof are highly objectionable. For instance,in thecase of proofed sheets which are to be used in that form orthat ofwaterproofed clothing, rubberized fabric gloves,

bathing shoes, light overshoes, and manyother articles, the loss inflexibility is'a serious defect, and where the fibrous material isdirectly exposed to view the appearance may be seriously affected. 1 Thecomparatively rapid ageing is also obviously a defeet in such cases.Moreover, when articles are rubberized as a whole by the dipping methodthere is serious objectioitto' the use of the ordinary-cementsmade frommilledv or' broken-down rubber for this purpose. Due to theextremely'high viscosity of'cements containing a relatively small amountof rubber, it is necessary to use a rather thin cement for the dippingoperation with the result that onl a very thin coat of rubber can beapplie by a single operation, there is the additional objection of theloss, fire risk, and injury to the health of the operatives, by reasonof the use oi: volatile organic solvents. Moreover, the milled orbroken-down rubber deposited. from such solvents is lacking in thestrength possessed by the natural latex rubber and it. does not asfirmly unite with the fibres of the material. t

An object of my invention is to provide a simple and economical processfor coating articles of fibrous material, whether in sheet or otherform, with'vulcanizable material.

Another object is to provide a coating method capable of makingrelatively heavily rubberized articles with a minimum number of coatingoperations.

Still another object is to provide a method of latex rubberizing fibrousmaterial which is capable of being successfully carried out by the useof the present types of spreading machines employed for s reading doughsmade from milled and bro en down rubber.

Still another object is to provide a method for rubberizing fibrousarticles by the use of rubberlatex in a thickenedform withoutsubstantial penetration of the material.

A further object is to provide a method for rubberizing fibrous articleswith a minimum loss of flexibility.

A. still further object is to provide a superficially rubberized fibrousarticlehaving the qualities of cheapness, flexibility, strength, age andwear resistance, and water tightness.

The invention consists broadly in coating '21 fibrous material with a'strongly adhering but substantially superficial covering of rubber inthe form of a water dispersion, and curing. The invention also includesthe article produced, having the properties of flexibility, age and'wear resistance, cheapness and strength.

In the carrying out of the invention any a suitable fibrous materialmaybe used, such as woven or knitted fabric, weftless cord fabno, feltedmaterial, or other fibrous material such as leather, either in sheet orother form.

Various rubber latices may be used, the latex most frequently employedbeing that of Heoeab'r'asz'lzensz's, and an artificial water dispersionof rubber is also applicable. The latex as obtained from the trees orplants varies considerably in its solid content, due

to the variety and age of the plant or tree, conditions of soilandclimate and other variables, but in the case of Hevea latex from 30to 35% solid content may be taken as a fair average. By my invention thelatex or other, water dispersion of rubber is first treated to obtain itin a-thickened, more or less plastic form, as by concentrating, physand-ical orchemical thickening of the latex by the use of certain agents,compounding, or by" a combination of any two or all of these methods.The latex may be concentrated in any desired manner, for instance asdisclosed in patent to McGarack No. 1,523,821, Jan. 20, 1925. The degreeofthickening required will depend on a number of conditions, such as thecharacter of the fibrous material to be treated, the nature of theparticular latex or other dispersion used, the thickness of the coatingdesired, the manner in which it is to be applied, and other variables.found that by using such a thickened latex or dispersion for the coatingit may be ap-; plied without substantial penetration of. the fibrousmaterial, andin all cases, irrespective of the method used for thethickening or for applying the coating,

weight, is combined with various types of mineral fillers, softeners,vulcanizing ingredients, possibly stabilizing agents, etc.. A specificcompound is as follows:

100 parts of dry rubber by weight (as concentrated latex containing say50% rubber by weight) w 200 parts of whiting by weight 10 parts of zincoxide by weight 4 parts of sulphur by weight 10 to 25 parts of spindleoil by weight 5 parts of glue 5 to 12,parts of 2% seap solution byweight The latex employed contains about 1 to 3% of ammonia, Which isordinarily used as a preservative upon shipment of latex from its sourceto a distant consumer. The above combination is made as follows: Thespindle oil is emulsified in' one-half its volume of a 2% soap solutionwith constant stirring. Thereafter the glue in the form of a 50% watersolution is added. The glue stabilizes the oil emulsion, and thewhiting,-zinc oxide and sulphur may now be added. The mixture is thenthor oughly incorporated by passing it through a paint or paste mill ofan ordinary type and from which it is then allowed to drop directly asit issues from the mill into the concentrated rubber latex, the latterbeing stirred continuously during the mixing.

The mass thickens on standing after a few hours, which is an advantagein the spreading operation. The compound'as so prepared is ready to bespread. This operation consists in laying a thin layer of the mixture 1have the consistency of the latex or dispersion or its compound shouldagent to prevent coagulation.

may be applied in the-same way. The cloth so coated is then dried; Byslightly inat substantially the same rate as that em-' ployed in theusual spreading process employing rubber cements or doughs. Such acoated clothmay be vulcanized by painting or spraying it with a solutionof a vulcaniz- 'ing mixture, for example a mixture containing 0.5 partsof zinc butylxanthogenate and 0.4 parts of (libenzyl amine dissolved in100 parts of carbon tetrachloride may be applied to the cloth bypainting or spraying. The spreadcloth so painted or sprayed is allowedto stand for one-half to one hour. The coated fabric is then heated forone hour at 212 F. at the end. of which time vulcanization isaccomplished. The proportions of vulcanization accelerators used may ofcourse be increased if desired.

.It will be observed in carrying out the above procedure that latexcontaining approximately 50% of solid content ha'sbeen employed, It willbe obvious however that latex of variable solid content may be usedinstead of that given in the preferred example. Latex containing 65% ofsolid matter has been employed to give good results.

Concentrated latex of much lower viscosity than the doughs and cementsordinarily used for spreading and dipping has a very much higherproportionate rubber content, hence where a relatively thick coating isdesired it may be obtained with fewer coating operations.

Although the process has been described including the application of avulcanizing agent after spreading the latex, it will be observed thatvulcanizing ingredients may be incorporated in the latex prior to itsapplication. A typical compound whichmay be s spread includingvulcanizing ingredients adapted to accomplish vulcanization 1s:

The compound is spread and dried as heretofore described andvulcanization is accomplished by allowing it to stand at approxi-.

mately 7 0 F. for one week. The time for vulcanization may be decreasedby increasing the quantities of accelerating agents. If desired theabove formula can be altered by replacing the butyl xanthogenate by thecondensation product of ethylamine formalde- 11 de'.

Another method ofvulcanization which may be employed consists inpainting or spraying one or more of the vulcanizing in gredientssubsequentto spreading and then exposing the spread material so treatedto another vulcanizing ingredient. For example,

. hour, whereupon vulcanization is secured.

'It will be understood that the temperature of vulcanization employedmay be varied in accordance with the compound vulcanized. ()rdinary roomtemperatureapproximately l* .or other temperatures above, below' or atthe normal hot vulcanization temperature may be employed. By the hotnormal vulcanization temperature is meant temperatures lyingapproximately between 240- 286? F.

Any of the fabrics so prepared may be used to produce a single plyfabric, or two fabrics coated by any of the methods may be placed faceto face to form two ply fabric in the regular way. a

As another example of a compound for coating by spreading, but with alatex thickened and stabilized by concentrating, compounding andtreatment with a specific thick-. cning and stabilizing agent, thefollowing is given: 10p parts rubber (as-60% solids latex) 100 partslithopone parts baryt es 10 parts glue 7 parts ammonium stearate 0.5part ultramarine blue part zinc oxide 3 parts sulphur 0,5 part zincdimethyl-dithio carbamate (dry basis) This compound may be vulcanized inair in two hours at 212 F. In the above compound the ammonium stearateacts as a thickening and stabilizing agent.

As a further example of a compound for coating by dipping with a latexthickened by concentrating the following is given:

Rubber (as 60% latex) 1o0 lphur Zinc oxi Zine dimethyl-dithio carbamateTheabove compound is suitable for rubberizing; fibrous materialbydipping, such as sheet fabric, or articles built up or otherwise formedof fibrous material, such as fabric gloves, bathing shoes, boots,overshoes, and many other articles. One way of making such articles asgloves, overshoes, bathing shoes,'etc., is by stretching a woven orknitted lining over a form and then dipping in the above-mentionedcompound, or instead the lining may be made by'building up cut-toshapeparts andjoiningthem and then dipping as before. There is a considerablefield of use in the arts for a rubberized fabric glove of suflicientflexibility to permit ready ham-- dling of materials by the wearer. Suchgloves may be used in chemical plants forthe handling of corrosivematerials, and in any other place where a durable and waterproof gloveis desired. Articles coated with the last-mentioned compound may becuredin about onehalf hour at a temperature of 250 F. If desired, however,the vulcanizing and accelerating ingredients may be omitted and anunmixed concentrated latex used instead. After coating the article withthe unmixed latex it may then be cured by a suitable curative such assulphur chloride, nitrogen sulphide N 8 or other suitable combinations,preferably those vulcanized at a comparatively low temperature, and whennecessary the cure may be accomplished by the use of hot air, steam, orhot glycerine.

In certain cases it may be desired to rubberize without impregnation.loosely aggregated fibrous material or relatively wide mesh woven orknitted fabric, and in other cases it may be desired to coat with arelatively thin or uncompounded latex. In'this event, as an aid inpreventing penetration or impregnation, the material may first bewaterproofed to a certain extent or rendered water-repellent in anysuitable manner. For example, an initial layer of cement having thefollowing constitution may be applied to the cloth :-rubber 100 part-s,lithopone (30 parts. zinc oxide 10 parts, sulphur 3 parts, parafiin 1part, dissolved in 400 parts of gasoline. After the application of thisinitial layer, the latex may be appliedwithout danger of penetration.However, the material may be rendered waterproof or water-repellent inany other suitable manner. It is obvious that if desired the materialmay be treated in a similar manner in any of the previously givenexamples.

The process is an economical one, eliminating as it does expensive,inflammable and toxic solvents such as solvent naphtha, gasoline, etc.,heretofore employed in cements. The process employing latex furthermorepossesses the advantage that the rubber coating is made up of materialwhich has not been subjected to the ordinary washing and millingprocesses usually employed in the preparation of rubber for theproduction of rubber cements, and it further contains all the solidconstituents of the latex. Such latex rubber is of superior strength andis very strongly bonded to the fibrous material, hence, even though bythe present coating method the fibrous material is not substantiallypenetrated or impregnated, the bond between the coating and material isstill a strong one with a resistance to strippingequal or superiorto'that obtained by the usual coating of such material with rubberdoughs or cements. By

reason of the non-penetration, of the fibrous material rubberized sheetsand other articles are produced having a maximum flexibility andresistance to ageing, and these qualities are particularly valuable inthe low cost production of many light rubberized fabric artisubstantialpenetration of cles such as waterproof clothing, aprons, hospitalsheeting, waterproof bags, footwear, gloves, and many other articles.The invention is also applicable to the coating of belting and fabrichose, in order to prevent their injury when exposed to the action ofchemicals, and also to increase their durability and strength.

While specific embodiments of the invention have been described, it isobvious that it is capableof wide application and I therefOredo not wishthe invention to be limited otherwise than as set forth in the appendedclaims.

Having thus described my invention what I claim and desire to,protect byLetters Patent is:

1'. The method of making rubberized articles of fibrous material whichcomprises coat-. ing normally penetrable fibrous material with athickened water emulsion of rubber without the material, and drying,thereby attaining a minimum loss of flexibility.

2. The method of making rubberized articles of fibrous material whichcomprises superficially coating normally penetrable fibrous materialwith a thickened and compounded water emulsion of rubber withoutsubstantial penetration of the material, and drying. .thereby attaininga minimum loss of flexibility.

V 3. The method of making rubberized articles of fibrous material whichcomprises coating normally penetrable without substantial penetrationthereof, with latex thickened by concentration, and drying the article.thereby attaining a minimum loss of flexibility.

4:. The method of making rubberized articles of fibrous material whichcomprises coating normally penetrable fibrous material with latex of 50it or higher concentration, and drying, thereby attaining a minimum lossof flexibility.

5. The method of making rubberized articles of fibrous material whichcomprises fibrous material coating normally penetrable fibrous materialwithout substantial penetration thereof with latex thickened byconcentration and compounding, and drying the article, thereby attaininga minimum loss of flexibility.

. 6. The method of making rubberized fabric articles of manufacturewhichcomprises relatively thickly covering normally 'penetrable fabric,without substantial penetration thereof, by a single coating operationwith concentrated latex containing low temperature curing ingredients,and curing, thereby attaining a minimum-loss of flexibil- 7. The methodof making rubberized fabric articles of manufacture which comprisesrelatively thickly covering-normally penetrable fabric by' a singlecoating operation with concentrated and compounded latex Withoutsubstantial penetration of the fabric interstices, and drying, therebyattaining a minimum loss of flexibility.

8. The method of making rubberized fabric articles of manufacture whichcomprises one of said coatings being directly in contact with thefibres.

Signed at New York, county of New York and State of New York, this 19thday of June, 1924:. I

ERNEST HOPKINSON.

forming on a normally penetrable fabric, a

relatively thick and uniform wear and waterproof covering of rubberthereon by a single spreading operation with concentrated and compoundedlatex Without substantial penetration of the fabric interstices, andcuring 'material with water repellent material to prevent substantialpenetration thereof by water, then superficially coating it with acoating material embodying rubber in water dlspersi on, and drying.

10. The method of making rubberized articles of manufacture whichcomprises superficially treating normallypenetrable fibrous I.thrgughout its depth.

material to render it water repellent, spreading thereon a plasticcoating embodying thickened latex, and drying.

11. The method of making rubberized articles of manufacture which,comprises superficially treating normally penetrable fibrous material torender it water repellent, spreading thereon a thickened plastic coatingemodving thickened latex and compounding.

material. drving and curing.

12. A flexible article of normal penetrable fibrous material having asan immediate coating attached thereto, without substantial penetrationof the material. the deposition product of a dried aqueous dispersionof-rub ber, said coating being 13. A vulcanized flexible and ageresistuniform in character ing article of manufacture formed of normal Ipenetrable fibrous material and .having an immediate attached coveringof the deposit from dried rubber latex and without substan-' vtialpenetration ofthe interstices ofthe material, said covering beinguniform in char;

acter throughout depth;

14. A flexible article of manufacture comv prising normal p'enetrablelfibrous. material having superposed, distinct and substantiallysuperficial coatings of water repellent material and the deposit ofadried water disdirectly ,in contact with the fibres.

15. A flexible article of manufacture com-- prising normal penetralo'lefibrous material 'having superposed, distinct and substantiallysuperficial coatings of water repellent material and the deposit ofdriedrubber late-x,

persion of rubber, one of said coatings being DISQLAIMER 1,784,523.EmestHopkinson, New York, N. Y. METHOD OF RUBBERIZING F1- nnovs MATERIAL ANDARTICLE PRODUCED THEREBY. Patent dated December 9, 1930. Disclaimerfiled May 20, 1939, by the assignee, United I States Rubber Company.

Hereby enters this disclaimer to each of claims 1 2, 3, 4, 5, 6, 7, 12,and 13 of said Lettersfatent.

[Qflicial Gazette June 13, 1939.]

